Astronomy & Space Science · AST-226
Io, Europa, Ganymede & Callisto: Foundations
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Overview
Physical identity of Io, Europa, Ganymede & Callisto
The four Galilean moons form a natural experiment in how distance from Jupiter, composition, tidal heating, and orbital history produce very different worlds. Io is intensely volcanic, Europa likely contains a global subsurface ocean, Ganymede is the Solar System's largest moon and has an intrinsic magnetic field, and Callisto preserves an ancient heavily cratered surface.
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References & evidence
Source library for this chapter
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- 01JupiterOpen source ↗
NASA Science
- 02Rings, Moons, and Pluto — SummaryOpen source ↗
OpenStax Astronomy 2e
View claim-by-claim traceability3 verified claims
The four Galilean moons form a natural experiment in how distance from Jupiter, composition, tidal heating, and orbital history produce very different worlds.
supported · checked Sep 22, 2026Voyager, Galileo, Juno, and Earth-based observations reveal active volcanoes on Io, disrupted icy terrain on Europa, Ganymede's magnetic field, and Callisto's cratered surface.
supported · checked Sep 22, 2026The Laplace resonance links the orbital periods of Io, Europa, and Ganymede, maintaining small orbital eccentricities that allow Jupiter's gravity to flex their interiors repeatedly.
supported · checked Sep 22, 2026